Means for holding a stamper plate in a molding metal die

ABSTRACT

An apparatus for holding a stamper plate in a molding metal die is provided which comprises a cavity plate having a cavity center hole, a stamper plate press member having a flange portion larger than the stamper plate center hole, a vacuum evacuation device, a compressed air supply device, a first connecting device for connecting the cavity center hole to the vacuum evacuation device, and a second connecting device for connecting the cavity center hole to the compressed air supply device. The stamper plate is mounted by inserting the stamper plate press member within the cavity center hole and the stamper plate center hole, such that the flange portion is engaged on the upper surface of the stamper plate and a space is formed between the stamper plate press member and the cavity center hole. The vacuum evacuation device is then connected to the cavity center hole through the first connecting device, so that the stamper plate press member is sucked into the cavity center hole. The stamper plate is removed by connecting the cavity center hole to the compressed air supply device through the second connecting device, so that the stamper plate press member is pushed out of the cavity center hole. A device for sucking the stamper plate onto the surface of the cavity plate can also be added.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a molding metal die for opticalsubstrates such as CD-ROMs and the like. More specifically, the presentinvention relate to a means for holding a stamper plate in a moldingmetal die for injection molding optical disk substrates pursuant to thepresent invention a stamper plate can be easily mounted on and removedfrom a disk cavity plate surface in the molding metal die.

2. Description of the Related Art

An optical disk substrate injection molding metal die for moving astamper plate press bush using a cam shaft is know in the prior art.Refer to, for example, Japanese Patent Application Laid-open No.H2-295726. FIG. 4 is a cross sectional view showing an injection moldingstate of a conventional optical disk substrate injection molding metaldie for moving the stamper plate press bush using the cam shaft.

FIG. 5 is a schematic cross sectional view showing a state in which thestamper plate press bush is moved by the conventional apparatus. Note,although these drawings show that a fixed side molding metal die islocated on an upper side, there are also cases in which the fixed sidemolding metal die is used laterally so that the center axis of a cavityis disposed horizontally and the position of the fixed side moldingmetal die is vertically reversed with respect to the above case.

A fixed side disk cavity plate 4 is disposed to a fixed side plate 6 anda hole 5 is defined at the center of the fixed side disk cavity plate 4to receive a stamper plate press bush 2. A flange 3 having an outsidediameter larger than the center hole of a stamper plate 1 is disposed atthe lower end of the stamper plate press bush 2. Further, a cutout 9 isdefined at the upper end of the stamper plate press bush 2. The fixedside plate 6 rotatably supports two engaging rods 7 to be engaged withthe cutout 9 of the stamper plate press bush 2. These two engaging rods7 have planes 8 each having a semi-circular cross section, and areconnected to each other so as to rotate in synchronism. A spool bush 10is inserted into the center hole of the stamper plate press bush 2 whichhas an injection hole 11 for molten resin at the center thereof.Ring-shaped cooling water passages 12 are disposed in the fixed sidedisk cavity plate 4 in contact with the fixed side plate 6.

A movable side disk cavity plate 17 is fixed to a movable side plate 19.A punch 18 is upward and downward movably supported at the center of themovable side disk cavity plate 17 to punch the center hole of a disksubstrate.

When injection molding is effected, the stamper plate 1 is engaged withthe stamper plate press bush 2 so that the outer periphery of the holeof the stamper plate 1 is pressed by the flange 3 of the stamper platepress bush 2. In injection molding, the stamper plate press bush 2 isengaged with the planes 8 of the semi-circular cross sections of the twoengaging rods 7 and pressed thereby, as shown in FIG. 4.

Next, the steps for removing the stamper plate 1 will be described withreference to FIG. 5. A molded disk substrate member 20 is removed byopening the die. When the two engaging rods 7 are turned in thedirection of the arrow as shown in FIG. 5, the planes 8 of the engagingrods 7 are disengaged from the cutout 9 of the stamper plate press bush2 and pushes the upper surface of the stamper plate press bush 2. Withthis operation, the stamper plate press bush 2 is pushed out from thecenter hole 5 of the fixed side disk cavity plate 4, as shown in thedrawing. Thus, the operator can take out the stamper plate 1 by handwhile holding the stamper plate press bush 2.

Since the conventional example is a system for mechanically mounting andremoving the stamper plate 1 by the stamper plate press bush 2, thestamper plate 1 can be securely mounted. However, since the above tworods 7 are used and a driving unit for driving them is needed, thefollowing problems arise. The use of the two rods 7 and the provision ofthe driving unit for driving them disposed in relation to the moldingmetal die prevent the reduction of size and weight of the die. Further,the provision of the above rods 7 and driving unit in relation to thedie restricts the design of the cooling water passages 12. Further, acertain degree of skill is required to mount and remove the stamperplate 1.

To solve the above problems, there is proposed an optical disk substrateinjection molding metal die provided with a vacuum suction type stamperplate press unit. Refer to, for example, Japanese Patent Publication No.H2-60502. As shown in FIG. 3, concentric circular grooves 22 and 23 aredefined around the central portion and outer peripheral portion of astamper plate side disk cavity plate 21. These concentric circulargrooves are connected to an external vacuum suction unit (not shown)through a communication hole 24.

A circumferential portion 27 to be inserted into the center hole of astamper plate 25 is disposed at the extreme end of a cylindrical bush26. A cylindrical bush 28 disposed at the center of the cylindrical bush26 is a punch for punching the center hole of the stamper plate 25. Aspool bush 30 is disposed at the center of a fixed side disk cavityplate 29. In the molding metal die arranged as described above, thestamper plate 25 can be simply removed from the stamper plate side diskcavity plate 21 by stopping the vacuum suction.

However, this type of apparatus also has a drawback. In the optical disksubstrate injection molding metal die, the interior of the cavity isoften filled with molten metal in the state that it is evacuated undervacuum to provide the density of the molten resin in the cavity withimproved uniformity. In this case, however, since the rear surface ofthe stamper plate 25 and the cavity are evacuated to the same level, nosuction force acts on the rear surface of the stamper plate 25.Therefore, there is a possibility that the stamper plate 25 will fallaway from the cylindrical bush 26 from the vibration and impact of themolding machine operating at a high speed. Further, a vacuum pump mustbe operated as long as the stamper plate 25 is mounted even if themolding operation is interrupted.

An object of the present invention is to provide a means for holding astamper plate in a molding metal die by a simple arrangement withoutemploying a special support structure in the molding metal die andpermitting the stamper plate to be easily replaced.

SUMMARY OF THE INVENTION

To achieve the above object, a means for holding a stamper plate in amolding metal die according to the present invention comprises a cavitycenter hole defined at the center of a cavity plate, a stamper platepress member including a flange portion having a portion larger than thecenter hole of the stamper plate at an end thereof and loosely insertedinto the cavity center hole from the other end thereof, a vacuumevacuation device, a compressed air supply device, andswitching/connecting means for switching and connecting the bottom ofthe cavity center hole to the vacuum evacuation device and thecompressed air supply device. When the stamper plate is to be mounted,the stamper plate press member is inserted into the cavity center holesuch that the other end of the stamper plate press member is insertedinto the center hole of the stamper plate and a space between the otherend and the cavity center hole is connected to the vacuum evacuationdevice by the switching/connecting means. When the stamper plate is tobe removed, the space between the other end and the cavity center holeis connected to the compressed air supply device by theswitching/connecting means to thereby push out the stamper plate pressmember.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view showing a main portion of a firstembodiment of an optical disk substrate injection molding metal dieaccording to the present invention;

FIG. 2 is a cross sectional view showing a main portion of a secondembodiment of an optical disk substrate injection molding metal dieaccording to the present invention;

FIG. 3 is a cross sectional view showing a main portion of an embodimentof a conventional optical disk substrate injection molding metal die forpressing a stamper plate by vacuum evacuation;

FIG. 4 is a cross sectional view showing an injection molding state of aconventional optical disk substrate injection molding metal die formoving a stamper plate press bush using a cam shaft; and

FIG. 5 is a schematic cross sectional view showing the state when thestamper plate press bush is moved by the conventional apparatus shown inFIG. 4.

DESCRIPTION OF PREFERRED EMBODIMENTS

A means for holding a stamper plate in a molding metal die according tothe present invention will be described in detail with reference to thedrawings. FIG. 1 is a view schematically showing the cross section of amain portion of an optical disk substrate injection molding metal dieusing an embodiment of the means for holding the stamper plate in themolding metal die according to the present invention and an air pressuredevice. Information to be transferred is held on the upper surface ofthe stamper plate 32 in the drawing. A stamper plate press member 31 hasan outside diameter to be accurately engaged with the center hole 33 ofthe stamper plate 32 as well as a flange portion 35 larger than thecenter hole 33 of the stamper plate 32 at the extreme end thereof.

A fixed side disk cavity plate 36 has a through hole 38 defined theretowhich has a hole 37 for accurately and detachably receiving the stamperplate press member 31. Further, the fixed side disk cavity plate 36 hasa hole 39 defined therein through which air is evacuated and supplied. Acylindrical cut bush 40 is a cut bush for punching the center hole of adisk substrate. A spool bush 41 is disposed at the center of thecylindrical cut bush 40.

A fixed side plate 42 has an externally connecting hole 43 definedthereto which corresponds to the air evacuation and supply hole 39. Theexternally connecting hole 43 is connected to a vacuum evacuation device50 and a compressed air supply device 51 through connecting means 53 and54, such as valves.

Note, numerals 44a-44d denote air tight seal members such as O rings andthe like.

Next, a mechanism for mounting and removing the stamper plate 32 of anembodiment of the optical disk substrate injection molding metal diewill be described. First, the stamper plate 32 is mounted in such amanner that the stamper plate press member 31 on which the stamper plate32 is mounted is manually inserted into the hole 37 of the fixed sidedisk cavity plate 36. Continuously, the vacuum evacuation device 50 isoperated by opening the connecting means 53 so that the air in the spaceof the hole 37 is evacuated though the externally connecting hole 43 asshown by an arrow and the pressure is instantly reduced to create avacuum. Therefore, the stamper plate press member 31 is strongly suckedinto the hole 37 of the fixed side disk cavity plate 36 and heldthereby.

Next, the stamper plate 32 is removed in such a manner that when thecompressed air supply device 51 is operated by opening the connectingmeans 54, the stamper plate press member 31 is pushed out from thecenter hole 37 of the fixed side disk cavity plate 36 by an airpressure. At that time, the operator can simply remove the stamper plate32 by hand while supporting the stamper plate press member 31. Note,although a means for sucking the stamper plate 32 to the surface of thefixed side disk cavity plate 36 is not shown in this example, it may beseparately formed as necessary.

FIG. 2 schematically shows the cross sectional view of a main portion ofan optical disk substrate injection molding metal die making use of asecond embodiment of the means for holding a stamper plate in a moldingmetal die according to the present invention and an air pressurecircuit. This embodiment is provided with a means for sucking a stamperplate 32 onto the surface of a disk cavity plate 46 in addition to astamper plate press member 31. Since the main components of thisembodiment are common to those of the aforesaid first embodiment, thecommon components are denoted by the same numerals as used in theembodiment 1 and the description thereof is omitted. A cylindricalmember 45 for sucking the stamper plate has an inside diameter which canbe accurately received by the outside diameter of the stamper platepress member 31.

Then, the outside diameter of the cylindrical member 45 has a pluralityof stripe-shaped rim portions which are accurately engaged with theinside diameter of a center hole 47 and a portion for forming amultiplicity of arc-shaped interval portions 48 in a radial portionwhich is 0.02 mm or more smaller than the radius of the above centerhole 47. The above rim portions are accurately engaged with the abovecenter hole 47 to thereby form a suction passage.

Next, operation of the second embodiment of the optical disk substrateinjection molding metal die will be described. First, the stamper platepress member 31 on which the stamper plate 32 is mounted is attached tothe inner diameter surface of the cylindrical member 45 disposed in thecenter hole 47 of the disk cavity plate 46 by vacuum evacuation. At thesame time, the air on the back surface of the stamper plate 32 and onthe disk cavity plate 46 is evacuated by a vacuum evacuation device 50from the above intervals 48 to thereby cause the stamper plate 32 tocome into intimate contact with the surface of the disk cavity plate 46.

Note, the stamper plate 32 may be inserted into the center hole 47 ofthe disk cavity plate 46 after it is coupled with the stamper platepress member 31 and the stamper plate press member 31 is engaged withthe cylindrical member 45.

The stamper plate 32 can be removed in such a manner that a compressedair supply device 51 is operated by actuating a valve of a connectingmeans 54 after a die is opened to thereby forcibly float the stamperplate press member 31 and the cylindrical member 45 at the same time.Then they are drawn out once and held.

Various modifications may be made within the scope of the presentinvention with respect to the embodiments described above in detail.

The optical disk substrate injection molding metal die using the meansfor holding the stamper plate in the molding metal die according to thepresent invention arranged as described above has the followingadvantages.

The optical disk substrate injection molding metal die does not need anactuator driving mechanism as used in the conventional optical disksubstrate injection molding metal die shown in FIG. 4 and FIG. 5. As aresult, the reduction in the size and weight of the molding metal diecan be achieved as well as a reduction in the number of components and awider degree of freedom of design. Thus, an optical disk substrateinjection molding metal die having better characteristics can bemanufactured.

The optical disk substrate injection molding metal die according to thepresent invention solves the problems of the removal of a stamper platecaused by vibration and the like which arise in the conventional opticaldisk substrate injection molding metal die shown in FIG. 3 employingonly vacuum evacuation.

What is claimed is:
 1. A means for holding a stamper plate having astamper plate center hole and an upper surface, in a molding metal die,said means comprising:a cavity plate having a cavity center hole; astamper plate press member having a first end, a second end, a flangeportion at the first end larger than the stamper plate center hole, andan outside diameter for engagement with the stamper plate center holeand the cavity center hole; a vacuum evacuation device; a compressed airsupply device; a first connecting means for connecting the cavity centerhole to said vacuum evacuation device; and a second connecting means forconnecting the cavity center hole to said compressed air supply device;wherein, the stamper plate is mounted by inserting said stamper platepress member within the cavity center hole and the stamper plate centerhole, such that said flange portion is engaged on the upper surface ofthe stamper plate and a space is formed between said stamper plate pressmember and the cavity center hole, and by connecting said vacuumevacuation device to the cavity center hole through the first connectingmeans, whereby said stamper plate press member is sucked into the cavitycenter hole; and wherein, the stamper plate is removed by connecting thecavity center hole to said compressed air supply device through thesecond connecting means, such that the stamper plate press member ispushed out of the cavity center hole.
 2. A means for holding a stamperplate in a molding metal die according to claim 1, wherein the stamperplate has an upper surface on which information is contained and thestamper plate is positioned such that the upper surface is horizontal.3. A means for holding a stamper plate in a molding metal die accordingto claim 1, wherein the stamper plate has an upper surface on whichinformation is contained and the stamper plate is positioned such thatthe upper surface is vertical.
 4. A means for holding a stamper plate,having a stamper plate center hole, an upper surface and a lowersurface, in a molding metal die, said means comprising:a cavity platehaving a cavity center hole; a stamper plate sucking cylindrical memberhaving an inner diameter, an outer periphery, a first end, a second end,a center axis, and a stamper plate sucking air passage forming portiondefined around the outer periphery and parallel to the center axis; astamper plate press member having a first end, a second end, a flangeportion at the first end larger than the stamper plate center hole, andan outside diameter for engagement with the inner diameter of thestamper plate sucking cylindrical member; a vacuum evacuation device; acompressed air supply device; a first connecting means for connectingthe cavity center hole to said vacuum evacuation device; and a secondconnecting means for connecting the cavity center hole to saidcompressed air supply device; wherein, the stamper plate is mounted bypositioning said stamper plate press member within the stamper platecenter hole and the inner diameter of the stamper plate suckingcylindrical member, such that said flange portion is engaged on theupper surface of the stamper plate, and by positioning said stamperplate sucking cylindrical member within the cavity center hole, suchthat the first end of said stamper plate sucking cylindrical member isadjacent to the lower surface of the stamper plate and a space is formedbetween the stamper plate press member, the stamper plate suckingcylindrical member, and the cavity center hole, and by connecting saidvacuum evacuation device to the cavity center hole through the firstconnecting means, whereby said stamper plate is brought into intimatecontact with said cavity plate; and wherein, the stamper plate isremoved by connecting the cavity center hole to said compressed airsupply device through the second connecting means such that said stamperplate press member and said stamper plate sucking cylindrical member arepushed away from the cavity center hole.
 5. A means for holding astamper plate in a molding metal die according to claim 4, wherein saidstamper plate sucking air passage forming portion has a radial length ofat least 0.02 mm.